Process of electrodepositing metals.



PATENTED MAR. 28, 1905 E. 1). KENDALL. PROCESS OF ELEOTRODEPOSITINGMETALS.

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UNITED STATES Patented March 28, 1905.

PATENT OFFICE.

EDWARD D. KENDALL, OF BROOKLYN, NEXV YORK, ASSIGNOR OF ONE- THIRD TOEDXVARD N. DIOKERSON, OF STOVALL, NORTH CAROLINA.

PROCESS OF ELECTRODEPOSITING METALS.

SPECIFICATION forming part of Letters Patent No. 786,221, dated March28, 1905.

Application filed October 28, 1903- Serial No. 178,883.

To (all whom, it may concern:

Be it known that I, EDWARD D. KENDALL, a citizen of the United States,residing in the borough of Brooklyn, in the city and State of New York,have invented a certain new and useful Improvement in Processes ofElectrolytic Deposition of Metals, of which the following is aspecification.

My invention relates to methods of deposit- IO ing zinc on metallic andother electricallyconductive surfaces, especially on surfaces of iron orsteel to protect the same from rust or corrosion, and particularlyrelates to electrolytic methods technically termed cold gal- 5 vanizingin contradistinction to ordinary so-called galvanizing by the use ofmolten zinc; and my process has for its object to use and efiect thedeposition of Zinc in required form from chemical solution which isincapable of spontaneous corrosive or chemical action on surfaces ofiron or steel and from which a regulated direct electric current of lowelectromotive force will deposit on cathodes of iron or steel or othermetal or on 2 5 other electrically-conductive surfaces a firm andadhering coating of pure zinc.

My invention consists in using with an electric current derived from avoltaic battery, or an electric generator of any suitable character andwith suitable electrodes an electrolyte containing zinc sulfoglycerate,which body I prepare, preferably, by'first acting on anhydrous or nearlyanhydrous glycerol with strong sulfuric acid, without or with theapplication of heat, to form sulfoglyceric acid, afterward diluting thisproduct with a limited quantity of water, and then saturating thisdiluted acid with Zinc, preferably by agitating the same with an excessof zinc oXid, or, better, with zinc hydroxid, finally adding more waterto form a comparatively dilute solution of zinc sulfoglycerate, theessential constituent of the electrolyte to be used in my process. If asomewhat-concentrated solution of this zinc sulfoglycerate be used aselectrolyte, the liquid has a high degree of electric conductivity, andan electric current of even less than one volt of electromotive forcewhen a zinc anode is used will suflice for the rapid deposition of Zinc,while a cur- 5 rent of considerably higher voltage, not ordinarilyconsidered excessive, with suflicient amperage, deposits the zinc toorapidly; but when a more diluted solution of the zincsulfoglycerate isused an electric current of increased electromotive force-say two orthree voltsis preferable, unless the electric resistance of the verydilute solution be diminished by addition of any suitable saltforexample, common sodium sulfate. From such a dilute solution of Zincsulfoglycerate, under influence of a properly-adjusted electric currentand with a suitable anode or anodes of zinc, the pure zinc deposited onpolished cathode-surfaces has remarkable smoothness 5 and uniformity. Ofcourse anodes of zinc are to be preferred for use in theherein-described process; but anodes of graphite may be substituted ifrequired for any purpose, with the disadvantage, however, that zinc isremoved from the electrolyte without replacement.

Electrolysis is facilitated by heating the herein-described electrolyte;but when used cold-21 e. at ordinary temperaturesthe rate 7 5 ofdeposition and the character of the deposited zinc are satisfactory andthe operation requires less supervision.

When a voltaic battery or a dynamo-electric generator is not available,an object may be covered with electrolytically deposited zinc withoutdeparting from my invention by submerging the said object in an aqueoussolution containing the zinc sulfoglycerate in a vessel within which hasbeen placed a porous 5 cell containing any suitable eXcitant for anelectropositive element therein immersed and consisting of zinc or othersuitable metal electrically connected with the said object.

A simple form of plant with which my proc- 9 ess may be conducted isshown in the accompanying drawing, which is aview in perspective of anelectrolytic tank containing the galvaniziiig solution with necessaryappurtenances. A is the said tank; B B, metallic rods electricallyconnected with the source of an electric current, on which the anodesare suspended in the electrolyte; O, a metallic rod having suitableelectric connection, on which the articles to be galvanized aresuspended, the same acting as cathodes; D, the source of an electriccurrent.

What I claim as my invention, and desire to secure by Letters Patent,is-

1. The herein-described process of electrolytically depositing metalliczinc, which consists in the electrolysis of an aqueous solutioncontaining zinc-sulfoglycerate by means of a suitable body acting as thecathode opposed to a suitable anode, both electrodes being electricallyconnected with the source of an electric current, substantially asdescribed.

2. The herein-described process of electrolytically depositing metalliczinc in the form of a hard adherent coating or plating on sur-

